There are of course lots of multichannel amps, but AFAIK, they are all typical power amps. They may or may not have input stage gain controls on each channel but will not have an overall volume control, and few if any would accept digital input. You'd basically need to design a significant part of the heart of a receiver.preamp -- the digital decoding system that figures out which codec is coming in, decodes to PCM if necessary then goes to the DAC, which is not something that I think many power amp buyers want (if only because of the RFI and heat problems a high output power supply not to mention multiple power amps might cause the more delicate processing section). It can be done, at least theoretically. IIRC, at least Mackie had a fine-sounding biamped self-powered studio monitor that would take pcm (although I don't recall if it was optical, coax or both) but also used regular old analog connections. But that's a one channel per device thing . . . .
So I'm pretty sure the answer is just plain no. But if one existed you could count on it being priced at the bleeding edge of the high priced stuff, if only because after you've designed the thing, spent a few tens of thousands of dollars to get UL or whatever EU or asian approval you need to sell the thing, set up a manufacturing line, etc., you're not likely to sell 100 of them . . . and somebody has to pay to recoup those sunk costs unless they're in the narrow market audio charity business.